Method for producing bituminous substance such as a coal tar pitch

ABSTRACT

A method for producing bituminous substance such as coal tar pitch which comprises adding sulfuric acid to coal tar produced by a high temperature dry distillation of coal and a bituminous substance produced from the coal tar, then adding petroleum heavy oil to the mixture to precipitate and separate pitch component.

i United States Patent Kishi et al.

[ Nov. 27, 1973 METHOD FOR PRODUCING BITUMINOUS SUBSTANCE SUCH AS A COAL TARPATCH Inventors: Chiyozo Kishi; Mitsuo Tatsuta;

Masayoshi Nago; Kanji Kibuishi; Yoshio Hatakeyama; Kaoru Miyakawa, all of Muroran, Japan Nippon Steel Corporation, Tokyo, Japan Filed: Nov. 5, 1971 Appl. No.: 196,096

Assignee:

Foreign Application Priority Data Nov. 10, 1970 Japan /98979 Nov. I0, 1970 Japan 45/98980 Nov. 21, 1970 Japan 45/102970 US. Cl 208/45, 208/6, 208/8, 208/39, 208/44 Int. Cl. Cl0c 3/02 Field of Search 208/8, 39, 44, 45, 208/6 Viscosity (cp) l I t [56] References Cited UNITED STATES PATENTS 2,560,642 7/1951 Greaves et al. 208/44 3,490,586 l/l970 Jaisle l,722,872 7/1929 Weindel..... 2,299,469 10/ l 942 DAmal 3,692,663 9/1972 Veda et a]. 208/44 Primary Examiner-Delbert E. Gantz Assistant Examiner-Veronica OKeefe Attorney-David Toren et al.

[5 7] ABSTRACT A method for producing bituminous substance such as coal tar pitch which comprises adding sulfuric acid to coal tar produced by a high temperature dry distillation of coal and a bituminous substance produced from the coal tar, then adding petroleum heavy oil to the mixture to precipitate and separate pitch component. 1

2 Claims, 2 Drawing Figures Temperature ('C) Y Viscosity (cp) PM ENTEU NOV 2 7 I875 3.775289 SHEET 2 EF 2 Temperature ('C) H] INVENTURS c 1 020 ms "h AWG WA "56 ma 49: g mo HA K VA METHOD FOR rnopucrnc BITUMINOUS suBs r scE SUCH AS A COAL TAR PITCH The present invention relates to improvements and relating to production of bituminous substance from coal tar such as pitch for pitch-coke and common pitches from coal tar.

According to a conventional method for producing bituminous substance such as pitch from coal tar, low boiling point aromatic components are removed by distillation or steaming, and if necessary polycondensation reaction is caused by a heating treatment or by blowing in the air to a certain desired degree, or distillated oil from creosote oil and the like is cut back to obtain bituminous substance of desired properties (viscosity and softening point).

Further, although the air blowing-in or the addition of sulfur can promote the poly-condensation and increase benzole-insoluble component, these measures are nothing more than auxiliary means for the heating treatment since they are effective only under a heated condition between 300 to 400C due to their reaction temperature.

Namely, it is impossible to blow in the air in an excessively large amount or to make addition of a large amount of sulfur in view of the softening temperature and so on.

Thus it has been eagerly sought for a method for improving the' quality of pitches which can freely control the above properties, particularly the relation between the benzole-insoluble component and the quinolineinsoluble component.

The present inventors have completed a method for achieving the above object, in which waste sulfuric acid (waste sulfuric acid produced in the washing step with concentrated sulfuric acid of crude benzole and petroleum products and is called merely as waste sulfuric acid hereinafter) composed mainly of sulfonic acid and organic compounds of sulfuric acid, or concentrated sulfuric acid is used as catalyst for the polymerization improvement of pitches, and this method can achieve the object at a lower reaction temperature.

According to this method, it is possible to increase freely the benzole-insoluble component without increasing the quinoline-insoluble component, but this method has a defect that the increase in fixed carbon content which is an important factor showing the quality of pitches is rather small.

The present inventors have completed a method which overcomes completely the above defect by an extraction treatment using petroleum heavy oils.

it has been conventionally known that sludge-like product is precipitated when a petroleum solvent is added to pitches. But this precipitate contains a large amount of solvent and takes a form of rigid granular sludge, and thus can not be taken out as tar pitch continuously on a commercial scale. Accordingly it has never been contemplated to produce and utilize tar pitches by this method.

However, this method just mentioned has a problem in separation of the precipitating pitch component and the extracted petroleum solution, and under a certain condition a small amount of the petroleum heavy oil mingles into the precipitating pitch component. In this case, the quality of pitch is shown by an excessive lowering of the fixed carbon content, and it is necessary to carefully establish the conditions such as the temperature, the mixing and extracting ratio, etc.

The present invention has also overcome this problem completely and makes it possible to produce pitches of good quality under a wide range of conditions in spite of differences in the quality of coal tar and properties of heavy oils.

In summary, the present invention is to provide a method which can maximize the extractability of lowmolecular components and the separability of pitch component by using petroleum hydrocarbons containing or mixed with a small amount of low boiling point saturated hydrocarbon oil in addition to high boiling point petroleum heavy oil as extracting agent for removing low-molecular low-boiling point components in the coal tar.

The petroleum solvents used in the present invention have the following properties. The aniline point more than 20C (desirably more than 40C). The boiling point range: the distillation ratio from the initial distillation point 200C is 0 30 percent, the distillation ratio from 200- 360C is 20 98 percent and the distillation ratio above 360C is 0 percent.

The petroleum solvents within the above range include light oil, heavy oil, mixtures of light oil and heavy oil, mixtures of heavy oil with light oil, kerosene and gasoline, etc., and various crude oils.

When the extracting agent contains a low boiling point saturated hydrocarbon in addition to the high boiling point heavy oil, the separability is improved due to the lowering of viscosity at the time of extraction, and part of paraffin or naphthene hydrocarbon oil which dissolves into the pitch layer in a very small amount is converted into a low boiling point hydrocarbon and thus distillation separation for final adjustment of softening point is easily attained.

When liquid petroleum gas or a low boiling point hydrocarbon oil (gasoline) alone is used as the extracting agent, it is necessary to give pressure in order to maintain the liquid phase, because of the heating which is required to take out the pitch component in the liquid form after the extraction, and extraction and separation of low molecular aromatic components which are unnecessary for the pitch is not satisfactory.

The present invention has eliminated the both defects and makes it possible to produce pitches of good quality from coal tar components with a simplified equipment.

The present invention shall be described in detail in reference to the attached drawings:

FIG. 1 is a graph showing the relation between the temperature and the viscosity of pitch produced 'by the present invention in comparison with that by a conventional method.

FIG. 2 is a graph showing the relation between the temperature and the viscosity of road tar produced by the present invention in comparison with that by a conventional method.

The references to heavy oils of grades A, B and C refer to the definitions of these grades pursuant to .118 (Japanese industrial Standards) as follows:

Heavy Oil-J18 K-2205-1960 Class 1(A) Class 3(0) Process for Category No. 1 No. 2 Class 203) No. 1 No. 2 No. 3 No. 4 test (JIS) Reaction Neutral K2252. Flash point, 0.. Excess 60 Excess 70- K2265. Kinematic viscosl est Less than 20.. Less than 50.. 50-150..... ISO-400.... Less than 400. K2283. l'our point. C Less than 5.... Less than 10 K2269. Carbon residue, wt. percent- Below 4 Below 8 K2270. Moisture, vol. percent Below 0.3 Below 0.4 Below 0.5. low K2275.

S component, wt. percent.-. Below 0.5. Below 2.0. Below 3.0. Below 1.5- Below 8.5. Below 1.5..- K2263 or 2273. Ash component, wt. percent Below 0.05-..- Below 0.1- 272.

EXAMPLE 1 EXAMPLE 4 Petroleum heavy oil of C grade was added to coal tar in a ratio of l l and the mixture was stirred at 50C and 100C respectively and left still at the above tem- Heavy oil of C grade was added to soft pitch and the mixture was stirred at 80C and 150C respectively. Pitches thus separated show the following properties.

TABLE 5 Percent Treating conditions Softening Bcnzole- Quinollne- Yield in atio of heavy oil to soft Temp., point, Fixed insoluble insoluble respect pitch C. carbon component component to tar Material soit pitch 34 38. 8 9. 2. 4 l/l 80 66 42. 0 27. 4 8. 2 59 1/1. 150 88 57.0 33.5 9.5 30 l/2 150 120 54. O 34. 9 9. 0

EXAMPLE 5 peratures. The pitches thus separated have the following properties.

TABLE 1 Softening Percent point (Mercury Benzole- Yield in method, Fixed insoluble respect Treating temp., C. C.) carbon component to tar EXAMPLE 2 The pitch produced by treating it at 50C in Example 1 was further distilled, and thus obtained pitch has the following properties.

TABLE 2 Softening Percent point (Mercury Benzole- Yield in method, Fixed insoluble respect Distillation temp., 0. C.) carbon component to tar Up to 340 67 50. 6 23. 2 29 Up to 363 88 57. 8 29. 3

Analysis of properties of the material coal tar used in this example and the pitch produced by a conventional method are shown in Table 3.

The pitch produced by the treatment at 50C in Example l was further treated at 150C with addition of heavy oil of C grade in a ratio of l l. Pitch thus separated shows the following properties.

'lABLE 4 Percent Benzole- Yield in Soltening point Fixed insoluble respect (Mercury method, 0.) carbon component to tor Heavy oil of C grade was added to soft pitch in a ratio of l 1 and the mixture was stirred at 150C. Pitch thus separated was washed with gasoline and dried. The product shows the following properties.

TABLE 6 Percent Benzole- Quinollne- Fixed insoluble insoluble Soitening point, 0. carbon component component EXAMPLE 6 Heavy oil of C grade was added to middle pitch in a ratio of l l and the mixture was stirred and left still. Pitch thus separated has the following properties.

TABLE 7 Percent Soitening Benzole- Quiuoline- Specific point, Fixed insoluble insoluble gravity. Samples C. carbon component component 38,"38 C.

Middle pitch 66.9 46.5 12.1 1.2 1,263 Pitch treated with 0 grade heavy 011 88.0 54. 5 32. 7 J. 0 1. 285

EXAMPLE 7 A grade heavy oil, B grade heavy oil and C grade heavy oil were added to coal tar respectively in ratios shown in Table 8 and the mixtures were stirred and left still at C. Soft pitch thus separated was distilled up to 320C and thus obtained pitch has the following properties.

TABLE 8 Percent Soitcning Bcnzolc- Quinollne- Yield in Tar/heavy oil point, insoluble insoluble Fixed respect to ratio 0. component component carbon coal tar A grade heavy oil, 1/0.5 ill 26.!) 6. 8 50. G 35 B grade heavy oil, .5 88 25.2 5.1 57.6 30 C grade heavy oil, 1/1 92 32. 3 7. 7 58. 7 53 EXAMPLE 8 TABLE 12.-ADDITION OF WASTE SULFURIC ACID TO SOFT PITCH C grade heavy 011 was added to coal tar in ratios of 1 1 and l 0.5 and the mixtures were stirred and left lament still at 70C and 50C. Thus separated bituminous Specific Soften- Benzole- Quinoline- Addition of gravity, ing insoluble insoluble products were analyzed for their properties to meet the 5 waste sulfuric 30 30 point, compocompo- Fixed standards of road tars, and the results are shown under. Percent can) Table shows the properties of the pitches pro- 1. 229 34.4 9.53 0. 40 38.38

duced by the present invention it; cortnhpirison with {g 245:: g??? gig 221% 1. .1 .4 4 those produced by the conventiona me o L 291 45. 2 34 37 276 4273 Further in FIG. Lthe curve I shows the temperature- NW A" V w 7 7 TABLE Heavgi Properties of road tars 0 treat- Percent ment Yield Fraction distillation test, Tar/ temperof road Specific Naphtha- Toluene- Flash percent at Experiment heavy ature, tar, EVT, gravity, Acid oil lane incoluble point, Foarn- No. oil ratio 0. percent /25 C. content content component 0. ing test 170 C. 207 C. 300 C.

1/1 70 60.4 1.1182 0.5 1.4 16.3 140 Good--- 0 4.7 9.1 1 1 40 47.6 1.165 0.6 1.6 11.8 135 do. 0 6.5 14.8 1 0.5 37 4.2.2 1.162 0.0 2.0 10.2 132 do 0 7.2 15.2

TABLE w EXAMPLE Percent In this example, concentrated sulfuric acid and waste softening 136M019 Quinomw sulfuric ac1d are each added to coke pven tar and the poiniligg insoluble insoluble F d mixtures are maintained at 50 and l2O C and 1118 O com 0 C0111 O- 1X8 Grade C.) n nt ri nt carbon Surredfor mmutes' Conventional method: 25 TABLE l3.-ADDITION OF CONCENTRATED SULFURIC Middle itch 67 12.1 1.2 46.5 ACID TO TAR Hard p tch 88 27. 2 3.6 53. 4

Hard pitch (modified Stirring temperature by heat 87 35. 2 10. 0 57. 1 Amount of Inventive method: of addition, Middle pitch (Exampercent Analysis 50 C. 80 C. 120 C. p e 2) 67 23. 2 a. 1 50. 0

ddle pitch (Exam- 30 Benzole-insolnble component, per- 4.5 4.5 4.5 p e 71 20. 4 0.4 69. 4 cent. Hardgnitch (Exam- 0 Quinoline-insoluble component 1.8 1.8 1.8 e 88 20.3 7.0 57.8 Fixed carbon (percent. 30.4 30.4 30.4 Hard pitch (Exam- Viscosity (50 .)cp. 200 200 200 ple 5) 91 26.9 6.8 60.6 Benzgle-insoluble comp 8.5 8.2 9.1 OBI]. viscosity curve of a pitch produced by the conventional 35 0.5-

g g f mmpment' method (softening temperature C, heat treatment) g ggg zggg 3 2? a 3 3 &3 and the curve 2 shows the temperature-viscosity curve Benzole-insolubl e cmhbb'iinijii'c'r 9.9 12. 2 13.6 of a pitch produced by the present invention (softening 1.0 qgfgohnmsomble component 1. 6 L 2 L 5 temperature: 91.8C, C grade heavy 011 added in a ratio ment- 0 xed carbon, (percent 32. 7 32. 8 .0 of l 0.5, treated at 80 C). 40 V1scoslty(50 cp 380 740 1,060

As seen from FIG. 1, the pitch of the present invenggggl mmwnent tion shows lowered temperature-sensitivity as com- Q g scomponent, pared with that of the pitch produced by the convenlgxedear bogg, ercent 33.4 33.9 .5 tional method. This tendency is also observed in road Scoslty (5 cp 720 tar produced by the present invention, thus overcoming 45 6 the d f t of conventional road an TABLE 14.ADDITION OF WASTE SULFURIC ACID TO TAR FIG. 2 shows measurements of the temperature- Am Stirring temperature viscosity relation. 1 represents a viscosity-temperature gggfi curve of road tar produced by a conventional method Femt Analysis EUT 62C and 2 1'6 resents a ViSCOSit -tem erature Benzole'insoluble component, per- 4.5 4.5 4.5

P Y P 50 t curve of road tar produced by the present invention. As 0 Qfigoimgmsomble component 1. B L 8 1. 8 BI'OBH seen from FIG. 2 the temperature sensmvity of v scos F zed carbongmem m 4 3o. 4 m 4 it of road tar produced by the present invention IS giscos%t ;(501bl.)cp 50g 50% 2120 O clearly lower than that by the conventional method. 2 33 3 11 e c mponen per EXAMPLE 9 55 1 0 Quinolingz-insoluble component, 1.4 1.8 1.8 l u are 1 to 5 percent of waste sulfuric acid is added to mld- Figed ggrbon percent 32.0 33.1 34. 6 die pitch or soft pitch heated (0 100 to 1 10C, and stir- 500m (50 g f; 15 mmutes The results are Shown m Properties of waste sulfuric acid and concentrated a es an sulfuric acid are shown Table 15.

TABLE 11.ADDITION OF WASTE SULFURIC ACID TO 0 MIDDLE PITCH TABLE 15 Percent Percent Addition of waste Specific Soften- Benzole- Quinoliue- Sulionic Tar-like suiiuric gravity, ing insoluble insoluble acids and high acid, 30/30 point, compocompo- Fixed Total Sulfuric organic polym- 0. C. nent nent carbon sulfur 65 Specific acid esters of erized Water gravity, concensulfuric subcon- 1. 263 66.0 12.11 1.22 46. 46 0.38 15/4 C. tration acid stance tent 1. 270 72. 2 18. 00 2. 46 47. e3 0. 5B 1. 282 76. 0 22. 71 2. 8B 48. 03 Waste sulfuric acid- 1. 4s 37 31 2s 1 1. 282 77. 7 27. (i4 2. J0 48. 43 0. J0 Concentrated sulfuric 1. 20a 78. 7 32. 07 2. 40 51. 41 ncld 1. s4 06 5 Yields of pitch in case when waste sulfuric acid or concentrated sulfuric acid is added to tar are shown in Table 16.

8 of precipitated pitch component, the temperature is preferably 50 to 150C in case of tar and 100 to 250C in case of middle pitch.

EXAMPLE 12 In this example concentrated sulfuric acid is added instead of waste sulfuric acid.

The raw material coal tar and, the properties of waste sulfuric acid and concentrated sulfuric acid, properties 'ffiiiii-i aoiseehaii'oa men" raoivr TXE of pitch and road tar produced by this example are shown in Tables 19, 20, 21 and 22.

Pitch properties Amount Heavy of added oil Percent waste Tar treatsulfuric heavy Grade of ment Yield of Softening Benzole- Quinolinc- Experiment acid, oil heavy temp., pitch, point, insoluble insoluble Fixed No. percent ratio 0 0. percent component component carbon 1.. 0 1/1 C 80 25 88 29.3 9.2 57.8 1. 5 1/1 C 80 95 34. 5 0.5 59. 9 1. 5 1/0. 5 G 80 28 88 36. 5 9. 6 59. 6 1. 5 1/0. 5 A 80 30 91 36. 9 9. 4 62. 7 1.5 1/0. 5 B 80 88 35.2 8.8 58. 6 5.0 1/1 C 120 46 1 83 1 58.2 8.6 l 51. 0 5.0 1/1 C 150 1 103 61.7 8.9 55. o 2. 0 1/1 C 32 111 39.0 8.7 59. 6 1 0. 5 1/1 C 28 87 30. 5 9. 5 58. 8 I 1. 0 1/1 C 80 28 80 32. 0 9. 4 58. o

1 Values for separated substances after heavy 1 Concentrated sulfuric acid.

Viscosity Specific gravity, iii/4 0.

EXAMPLE 1 1 Amount of added waste sulfuric a d,

Heavy 01 Yield Grade treatof of ment heavy temp.,

011 0. percent h Tar/ eav ratio Experiment No.

EVT, percent C.

Specific gravity, 1 2.5/25 0.

oil treatment without distillation for adjustment of softening flair: it-raw MATERIAL COAL TAR Percent Fraction distillation test at- Quinoline Benzoleinsoluinsoluble ble component Tar acid content Fixed carbon component e content 'ITKBLEHWFPROPERTIES OF PITCH BY CONWBIQXL METHOD Percent Benzoleuinollne Softening insoluble nsolublo point, 0. component component Middle pitch Hard pitch Hard p tch (modified by heat) ""flamis rabwcer6N OF ROAD TAR FROM TAR Properties of road tar Percent Toluene- Acid Naphincoluble oi thalene comcontent ponent Fraction distillation test, percent at Flash point, content C.

Bananas-Separated substance (precipitate) after the heavy oil treatment was analysed as road tar and distillation or oil addition for adjustment of viscosity was not conducted.

mfia aaefi tease more 'Ta R 'B'Y coaveimoarn'mamob Toluene- Speciflc Naphinsolu- Flash Fraction distillation test atgravit Acid oil thalene ble compoint, Form- EVT, C 15/4" content content ponent C. ing test C. 270 C. 300 C. 59.7 1.23 0.2 Trace.-. 11.7 174 Good 0 1.4 4.2

As seen from the Tables 17 and 18, the amount of EXAMPLE 13 added waste sulfuric acid or concentrated sulfuric acid has direct connection with increase and decrease of the benzole-insoluble component, and the proportion of heavy oil and the treatment temperature control the softening point, the fixed carbon content and separation from heavy oil.

The addition of heavy oil is preferably from 30 200 percent to the tar for good separation and accessibility Extraction by petroleum light oil alone or mixed Oil Petroleum light oil, heavy oil or mixed oil was added in various ratios to 10kg of coal tar, the mixtures were heated under stirring, left still and the pitch component which precipitated in the lower layer was analysed.

The results of this Example are shown in Table 22, and the material coal tar and the petroleum light oil and heavy oil used as solvent are set forth in Table 23.

TABLE 22 Properties of separated pitch Extraction condition Percent Mixing proportion Tcni- Soit- Bcnzolo Quinolino pcracning insoluinsolu- Specific Cool heavy Light turc, temp, Fixed ble comblo comgravity, Experiment No. tar oil (2) oil 0. 0 carbon poncnt ponent 30/30 0.

' Tiers Fraction distillation test Percent Initial Percent at- Benzole Quinoline Specific boiling Aniline insoluinsolu- Fixed grav it, point, 200 230 300 360 Dry point, ble comble comcarbon /4 0. 0. C. 0. point C. ponent ponent Coal tar 1.200 192 21 34 7.6 3.4 33. 5 Li ht oil 0.811 178 12 65 87 34.2 68 G eavy oil (2). 0.864 238 1 4 25 79 It is also clear from the above results that a pitch having high fixed carbon content can be obtained when light oil together with C grade heavy oil is added than when C grade heavy oil above is added. Further the properties of the solvent and the extraction conditions have a great influence on the separability and properties of the pitch.

EXAMPLE 14 Properties of solvent in the solvent-extraction of coal tar and separability of pitch component.

Similar experiments as in Example 13 were conducted on various solvents, and the results are shown According to the solvent-extraction of the present invention, the fixed carbon content in the pitch is increased, but the contents of bensole-insoluble component and B-resin component depend on the properties of the raw material coal tar because poly-condensation modification step by a heat treatment is not included as in the conventional method.

For solving the above problem, the present inventors have completed a method for producing pitch of very good quality by conducting poly-condensation after the addition of a small amount of waste sulfuric acid or concentrated sulfuric acid to coal tar at a low temperain Table 24. ture. One example of this method is set forth under.

TABLE 24 Properties of solvent Fraction distillation test Extraction condition Fixejd caron n Initial Percent et- Ratio precipi- Specific Aniline boiling separability teted gravitg, point, point, 200 360 Dry Coal Temp, of precipitated pitch, 15I4 0. 0. 0. point tor Solvent C. pitch percent 0 heavy oil (1). 0 921 52 1 1 80 Slightly poor.. 53. 8

o 0.921 52 1 0.5 P G heavy oil (2)- 0 864 79 1 1 Do 0.864 79 1 0. 5 B heavy oil.. 0.910 61 1 1 A heavy oil. 0. 839 72 1 1 Light oil 0. 811 68 1 1 Kerosene-.. 0.788 42 1 1 Gasoline 0. 736 10 1 1 Crude oil 853 54 1 1 Mixed oil 21);-.. 0. 826 77 1 1 Mixed oil 2) 0.866 19 1 1 Remark: Aniline point was 'meas'urea'wrfli distillated oil up to 360C.

The mixed oil is a mixture of C grade oil, light oil,

kerosene and gasoline.

As understood from the above results, it is a prerequisite for increasing the fixed carbon content in the separated pitch that the aniline point is high and a suitable amount of low-boiling point component is mixed. tillation).

Properties of pitch 5 l Percent o vent ratio Addition Qulno- Yield of of waste Crude Extrac- Soften- Benzoleline pitch in sulfuric oil or tion ing insoluble insoluble respect acid, Coal mixed temperopoint, Fixed compocompo- [3 to tar, Solvents percent tar oil ture, C. 0 carbon nent nent resin percent Crude oil 1 1 80 61. 0 33. 8 11. 0 22.8 34 D0 0. 5 1 1 80 87 59. 6 35. 8 8. 5 27. 3 48 0. 5 1 1 93 62. 3 42. 0 11. 5 30. 5 30 0. 5 1 0. 5 80 92 61.0 36. 8 11. 0 25.8 36 l 0. 5 80 89 58. 1 31. 0 8. 3 22. 7 47 1 0. 5 80 88 59. 0 37. 5 8. 1 29. 4 51 l 0. 5 80 85 56. 5 35. 1 6. 6 28. 5 55 1 1 80 96 59. 8 36.1 8.2 27. 9 49 1 0. 5 120 93 62.0 39. 6 10.0 29. 6 41 As above, the addition of waste sulfuric acid improves not only the benzole-insoluble component and B resin component, but also the yield of pitch.

These effects are same when sulfuric acid is used infrom the coal tar B. But by mixing light oil etc. to the solvent and further by adding waste sulfuric acid thereto, it is possible to produce pitch of high grade.

It is also possible to apply the present inventive stead of waste sulfuric acid. Table 26 shows the analysis 5 method to a soft pitch and a middle pitch as well as to of the waste sulfuric acid used in this example. the coal tar. This is shown in the following example.

TABLE 28 Properties of pitch Addition ratio to 1 of tar Percent Addition Extrac- Soitenof waste tion ing Benzolesulfuric heavy Light temp, point, Fixed insoluble Coal tar grade acid oil oil 0. carbon component TABLE 26.ANALYSIS OF WASTE SULFURIG ACID v EXAMPLE 17 Middle pitch and soft pitch Percent 20 The experiment was condacted in the same manner u fm ii as in the previous example except that kg of a mid- Sulfuric 0.55mi; dle pitch or soft pitch was used instead of the coal tar, S ecifie ravlt acid sultonated 3 a content Substances Tar water and C grade heavy or] alone or a mixed Oil of light Oil 29 4 1 was used as extraction solvent. The results are shown 1.486 52.23 28. 07 14- 5 in Table 29- TABLE 29 Properties of separated pitch Solvent ratio to 1 of material Percent Extrac- Soften- 0 tion lng Benzoleulnoline Bituminous heavy Light temp., point, Fixed insoluble nsoluble material 0 oi 0. 0. carbon component component As seen from the above, when the poly-condensation treatment with addition of sulfuric acid and the solvent in the solvent-extraction are selected suitably it is possible to produce an electrode pitch of high grade from a For comparison, the quality of the pitch produced by the present invention and the quality of the pitch produced by conventional methods are set forth in Table 30.

TABLE 30 Properties of pitches Percent Soften- Benzole- Quinollne insoluinsolupoint Fixed ble comble com- B Producing method carbon ponent ponent Resin Remark Mere distillation by conventional method 67 46. 5 12.1 1. 5 10.6 Same as above but with modification by heating. 87 57. 5 35. 2 10. 7 24. 5 Presnt invention, mixed oil used 89 58.1 31.0 8. 3 22. 7 Example 15 Present invetion, waste suliuric acid added (0.3%)

raw material coal tar having low contents of fixed carbon and solvent-insoluble components.

The effects of the present invention due to difference in coal tar qualities are set forth in the next example.

Specific Benzola- Quinoliii; gravity, Fixed insoluble insoluble Coal tar grade 15/4 0. carbon component component The experiment method is just same as in Example 15, and the results are shown in Table 28.

The results in Table 28 show that it is harder to produce pitch of good quality from the coal tar A than From the above examples it is understood that according to the present invention it is possible to produce a high grade pitch containing high fixed carbon content and benzole-insoluble component content (namely high in B-resin component content) without requiring a high temperature treatment with a low-cost equipment, thus the present invention has very large economical advantage.

Further by using petroleum crude oil, as solvent, it is possible to produce pitch at a very low cost, and the solvent after the extraction is a mixture of crude oil and low-molecular aromatic component of the coal tar, and thus can be readily used for production of petroleum products (gasoline, light oil, heavy oil and asphalt) by distillation.

Further, these petroleum products are enhanced in their qualities when mixed with aromatic component. For example, gasoline shows increase octane rating,

and asphalt shows improved mixability with aggregate materials and improved permeability when used for road pavement.

Also, the addition of waste sulfuric acid or sulfuric acid serves to prevent colouration of distilled oil and formation of gum substance at the time of distillation refinement of the separated extraction solvent and contributes for desulfurization, thus improving the quality of distilled products.

Although the object of the present invention is to provide a method for producing and improving coal tar, it is possible to produce unique petroleum products and low-sulfur fuel oil when coal tar is used as fuel or when the present invention is applied to the refining step of petroleum without heat decomposition and contact decomposition as conventionally done.

What is claimed:

1. A method for producing coal tar pitch comprising adding sulfuric acid to coal tar produced by the high temperature, dry distillation of coal and then adding a petroleum hydrocarbon oil to the mixture, said oil having an aniline point above 20C and consisting of 0-30 percent of a fraction having a boiling point up to 200C, 20 to 98 percent of a fraction having a boiling point between 200 and 360C and 0 to percent of a fraction having a boiling point above 360C, the ratio of coal tar to said oil being from 110.3 to 2.0, and maintaining the temperature between 50 and 250C to precipitate and separate the pitch component.

2. A method for improving coal tar pitch by extraction comprising adding to the pitch a hydrocarbon oil having an aniline point above 20C and consisting of 0-30 percent of a fraction having a boiling point up to 200C, 20 to 98 percent of a fraction having a boiling point between 200 and 360C and 0 to 80 percent of a fraction having a boiling point above 360C, the ratio of coal tar to said oil being from 110.3 to 2.0, and maintaining the temperature between 50 and 250C to precipitate and separate the pitch component. 

2. A method for improving coal tar pitch by extraction comprising adding to the pitch a hydrocarbon oil having an aniline point above 20*C and consisting of 0-30 percent of a fraction having a boiling point up to 200*C, 20 to 98 percent of a fraction having a boiling point between 200* and 360*C and 0 to 80 percent of a fraction having a boiling point above 360*C, the ratio of coal tar to said oil being from 1:0.3 to 2.0, and maintaining the temperature between 50* and 250*C to precipitate and separate the pitch component. 